The morphology development within a PS/LLDPE blend with 5 wt % of LLDPE at various stages of uniaxial deformation and after cessation of the flow was studied. Under given deformation conditions the dispersed LLDPE particles stretch and form highly elongated fibrils in agreement with a modified capillary number model. The morphology development after deformation was investigated for two different modes-relaxation and recovery. It was found that the stress in the sample is the crucial parameter determining the morphology development. During the first part of relaxation the stress in the sample is sufficient to hold the particles in the highly elongated state and, therefore, Rayleigh breakup takes place according to the Tomotika theory. It results in considerably finer phase structure. Contrary to this, in the absence of the stress in the sample, that is, in the recovery mode, the fibrils start to shrink immediately after the deformation and after a certain time the spherical morphology is restored. During elongation and recovery no evidence of coalescence was observed. (C) 2007 Wiley Periodicals, Inc.